Increasing number of electrophotographic type image forming apparatuses of a unit exchanging type in which the parts relating to the image formation are unified to facilitate the maintenance operation. Most of such image forming units (process cartridge) employs a contact charging type with which a charging roller as a charging member is contacted to a photosensitive member to electrically charge the photosensitive member. In such a process cartridge employing the contact charging type, an image defect may occur due to a deformation or the like of the charging roller if the apparatus is kept unoperated for a long term with the charging roller and the photosensitive member contacted to each other.
In order to suppression such an image defect, the process cartridge is shipped while spacing the photosensitive member and the charging roller from each other by a spacer. The spacer is dismounted by the user who mounts the process cartridge to the device.
Such a structure is cumbersome in that the user has to remove the spacer. If the user operates the image forming apparatus without removing the spacer, a sheet jamming and/or a transfer defect or the like occurs.
Japanese Laid-open Patent Application Hei 11-95532 discloses a structure in which a charging roller kept spaced from the photosensitive member is brought into contact to the photosensitive member by rotation of the photosensitive member. More specifically, the photosensitive member and the charging roller are spaced from each other by a sector gear (spacer member) fitted on a rotation shaft of the charging roller. With such a structure, when the photosensitive member is rotated, the sector gear rotates to contact the charging roller to the photosensitive member.
The process cartridge is vibrated during the transportation or the like from the factory shipment to the mounting to the apparatus. The above-discussed publication uses a sector spacer member which is point-contacted to the photosensitive member. Therefore, the vibration may disengage the spacer member with the result of unintentional contact between the photosensitive member and the charging roller.
To avoid the unintentional intention, it would be considered that the process cartridge is packed with buffering material during transportation. However, the buffering material is disposed after it is taken out of the process cartridge, and therefore, use thereof should be considered with great care. When the buffering material is used, the size of the package of the process cartridge is large with the result of a large load on the environment.
It is an object of the present invention to suppress unintentional disengagement of the spacer member attributable to vibration (falling in an extreme case) during transportation.